A device that measures a measurement subject's pulse rate (heart rate) by wrapping a belt to which an electrocardiographic sensor is attached around the measurement subject's chest area and measuring the beating of the measurement subject's heart electrocardiographically can be given as a conventional example of this type of device.
There is also a device that measures a pulse rate by detecting pulsatory motion in a measurement subject's blood vessel in a non-electrocardiographic manner, unlike the aforementioned device that electrocardiographically detects a measurement subject's heartbeat.
A device that measures a measurement subject's pulse rate by photoelectrically detecting pulsatory motion in a measurement subject's subcutaneous blood vessel using a photoelectric sensor can be given as an example of the latter type of device (see Patent Literature 1 (JP H10-234684A), for example).
In the latter type of device, a signal expressing pulsatory motion in the measurement subject's subcutaneous blood vessel (a pulse wave signal) is obtained and the pulse rate is measured based on the cyclic nature of fluctuations in the pulse wave signal over time.